1. Field of the Invention
The present invention relates to a process for controlling a travel state of a vehicle during braking, in which it is possible to perform an antilock brake control for eliminating a locking tendency of a wheel during braking, and to switch between a four-wheel drive state and a two-wheel drive state.
2. Description of the Prior Art
Such a process is conventionally known, for example, from Japanese Patent Application Laid-open No. 43325/87, in which the control of switching from the four-wheel drive state to the two-wheel drive state can be carried out during execution of the antilock brake control.
In a condition when all the four wheels are driven during execution of the antilock brake control, such a switching control is carried out because of a disadvantage produced due to the fact that braking forces for wheels interfere with one another during execution of the antilock brake control. However, when a depression force for depression of a brake pedal in the four-wheel drive state is small, all the four wheels may gradually fall into their locked states with the antilock brake control remaining not operating, i.e., with the four-wheel drive state being maintained. Even when the switching from the four-wheel drive state to the two-wheel drive state is not operating due to a problem such as breaking of a signal line or a problem in the actuation of switching the drive state, notwithstanding that the antilock brake control is operating, the four wheels may gradually fall into their locked states.